package gondole

import (

	"bytes"

	"encoding/json"

	"fmt"

	"io"

	"mime/multipart"

	"os"

	"path/filepath"

	"github.com/sendgrid/rest"

)

// UploadMedia uploads the given file and returns an attachment

func (g *Client) UploadMedia(filePath string) (*Attachment, error) {

	var b bytes.Buffer

	if filePath == "" {

		return nil, ErrInvalidParameter

	}

	f, err := os.Open(filePath)

	if err != nil {

		return nil, fmt.Errorf("cannot read file: %s", err.Error())

	}

	defer f.Close()

	w := multipart.NewWriter(&b)

	formWriter, err := w.CreateFormFile("file", filepath.Base(filePath))

	if err != nil {

		return nil, fmt.Errorf("media upload: cannot create form: %s", err.Error())

	}

	if _, err = io.Copy(formWriter, f); err != nil {

		return nil, fmt.Errorf("media upload: cannot create form: %s", err.Error())

	}

	w.Close()

	req, err := g.prepareRequest("media", rest.Post, nil)

	if err != nil {

		return nil, fmt.Errorf("media prepareRequest failed: %s", err.Error())

	}

	req.Headers["Content-Type"] = w.FormDataContentType()

	req.Body = b.Bytes()

	// Make API call

	r, err := restAPI(req)

	if err != nil {

		return nil, fmt.Errorf("media upload failed: %s", err.Error())

	}

	// Check for error reply

	var errorResult Error

	if err := json.Unmarshal([]byte(r.Body), &errorResult); err == nil {

		// The empty object is not an error

		if errorResult.Text != "" {

			return nil, fmt.Errorf("%s", errorResult.Text)

		}

	}

	// Not an error reply; let's unmarshal the data

	var attachment Attachment

	err = json.Unmarshal([]byte(r.Body), &attachment)

	if err != nil {

		return nil, fmt.Errorf("cannot decode API response (media): %s", err.Error())

	}

	return &attachment, nil

}